Initialization

The firebase.NewApp()
method can now be invoked without any arguments. This initializes an app
using Google Application Default Credentials, and
firebase.Config loaded
from the FIREBASE_CONFIG environment variable.

Authentication

The user management operations in the auth package now uses the
identitytoolkit/v3 library.

The ProviderID field on the
auth.UserRecord
type is now set to the constant value firebase.

Authentication

When deployed in the Google App Engine environment, the SDK can
now leverage the utilities provided by the
App Engine SDK
to sign JWT tokens. As a result, it is now possible to initialize the Admin
SDK in App Engine without a service account JSON file, and still be able to
call CustomToken()
and CustomTokenWithClaims().

Authentication

Now uses the client options provided during
SDK initialization to
create the http.Client that is used
to fetch public key certificates. This enables developers to use the ID token
verification feature in environments like Google App Engine by providing a
platform-specific http.Client using
option.WithHTTPClient().